Drilling bit with integral stabilizer

ABSTRACT

A rotary drilling bit having depending legs with rotary cutters journaled thereon, the legs terminating downwardly in relatively thin portions facing radially outwardly and the bit body being provided with hard metal wear-resisting stabilizer shoes integral therewith and preferably located vertically above the legs to resist lateral movement of the tool in the formation resulting from lateral movement of the drill string above the tool and thereby reduce wear of the tool legs, and especially their lower portions.

llnlte States Patent 3,158,214 11/1964 Wisler et a1 175/375 3,344,87010/1967 Morris 175/374 X 3,439,757 4/1969 Elenburg..... 175/3253,461,983 8/1969 Hudson et a1 175/375 Primary Examiner Ernest R. PurserAttorney-Allan D. Mocltabee ABSTRACT: A rotary drilling bit havingdepending legs with rotary cutters journaled thereon, the legsterminating downwardly in relatively thin portions facing radiallyoutwardly and the bit body being provided with hard metal wearresistingstabilizer shoes integral therewith and preferably located verticallyabove the legs to resist lateral movement of the tool in the formationresulting from lateral movement of the drill string above the tool andthereby reduce wear of the tool legs, and especially their lowerportions.

PATENTEU UECZI ml 4 INVENTOR l V/A/AM J A/6/450A/ A Tram/6MDlltllLlLllNG lBl'll WllTH INTEGRAL STABllLllZlER This invention relatesto drilling tools and more particularly to drill bits for drillingthrough rock and other hard formations in drilling oil wells. It relatesprimarily to rotary bits having depending legs with rotary cuttersthereon, the cutters being mounted on journals extending inwardly anddownwardly from the inner sides of the legs.

Drilling bits of this type are conventionally suspended from drill pipeextending downwardly from the drilling rig at the surface. Generally thestring of drill pipe is rotated by the drilling rig and this rotation istransmitted to the bit at the bottom of the hole. ln some cases rotationof the tool is accomplished through the use of a turbine or fluid motormounted on the bottom of string of drill pipe just above the bit. Ineither case the drill pipe or drilling string, being of less diameterthan the hole being drilled downwardly through the formation, is subjectto lateral whipping or other movement. This of course creates a certainamount of angularity to the string and it is imparted to a certaindegree to the drilling tool itself. In drill bits of the type mentionedabove, this results in a tilting of the tool which while of not greatangularity, causes excessive pressure of the lower portions of the legsof the bit against the rough rocky formation as the tool is rotated.Because of the dictates of limited space in which to accommodate therotary cutter on the bottom of the bit and the inward and downwardangularity of their journals, the upper ends of the journals, where theyextend from the bottoms of the legs, define leg bottom portions whichare quite thin when considered in the environment in which they operate.Because of the peculiarities of the bit structure, and particularly thelower portions of the cutter journal supporting legs, undue lateralswinging or rocking mo tion of the bit will greatly reduce the life ofthe tool since the lower portions of the legs will relatively rapidlywear away.

Stabilizers for the drilling string have been used heretofore but theyare located above the drilling tool and quite often some distance awayfrom it, so that the tool still has an opportunity to move or tiltlaterally. Stabilizers have also been used on subs located in the stringjust above the drilling bit but they are not located as critically closeto the bottoms of the legs of the bit as desired and it is by far betterdrilling practice to eliminate subs where possible. Additionally, a subwith stabilizing means thereon comprises considerable additionalstructure which is not only costly but requires labor in its addition tothe string.

It is a general object of the invention to provide means for stabilizinga drilling tool such as a drill bit having depending legs which reducein thickness at their bottom portions because of the nature of theirconstruction wherein the stabilizing means is not mounted some distanceabove the tool so that its effect is greatly lost but is mounteddirectly on and made integral with the body of the drilling tool so thatit is immediately above the leg structure it is intended to protect andforms a part of the tool body itself so that an extra structure, such asa sub, is not required. Another object is to provide a stabilizerlocated directly upon the body of a drilling tool which is of hardmetal, a term of art denoting carburized steel, a hard metal weldedoverlay or the like, so that the critical wear resisting stabilizingportions of the tool can be made much harder than it would be practicalto make the entire tool body.

It is customary to manufacture rotary tools of this type with theirbodies reducing in diameter upwardly to provide room for the escape ofcuttings and also to remove a major circumferential outer portion of thetools from wear producing contact with the formation being drilled. Thisconventional shape adapts itself quite well to the incorporation of mystabilizing means since wear resisting hard metal can be laid on theoutside of the body by welding procedures and/or hard metal elements canbe attached to the body by other means in thicknesses sufficient togreatly lengthen the life of the tool and still keep the overalldiameter of the upper portion of the tool within the limits provided bythe diametrical cutting path or bore described by the rotary cutters.

The above and other objects and advantages will more fully appear fromthe following description. in connection with the accompanying drawing:

lFlG. l is a more or less diagrammatic illustration of a portion of adrill string with a conventional drill bit or tool mounted on the lowerend thereof;

H6. 2 is a perspective view of a drill bit with the rotary cutter shownin broken lines and with an embodiment of my invention incorporated inthe body of the bit;

FIG. 3 is an enlarged sectional detail taken approximately on the line3-3 of FIG. 2.

In FIG. I there is illustrated a drill string, generally indicated at i,made up of the usual sections of drill pipe 6 threadedly connected andsuspended from and rotated by a drilling rig at the surface of theground. On the lower end of the drill string 4 is shown a drill bit 8which is of conventional type and the details of which are not set forththerein.

In FIGS. 2 and 3 there is shown a drill bit 10 which is similar to thebit of FIG. 1 except that it graphically includes the structure of myinvention. The bit it) includes a body 12 having an upper threadedextension M to which the lowest section of drill pipe is threadedlyconnected in the usual manner. Extending downwardly from the bit body112 are legs 16. As shown in FIG. 3, each leg It: has an inwardly anddownwardly directed journal 18 which is adapted to rotatably support acutter illustrated at 20 in broken lines. The cutter may be mounteduponball bearings 22 and additional bearing elements in a manner wellknown in the art. Customarily the bearing balls 22 are inserted througha passage 241 which is subsequently closed by a pin 26 secured by a weld23.

The base of the journal 13 is defined by a surface of revolution 30lying in a plane normal 'to the longitudinal axis of the journal ltd.Due to the fact that the cutters 20 must perform at least a part oftheir cutting action at or approximately at the outer diameter of thetool as a whole, the journal 18 is so located that the surface ofrevolution 30 defines a relatively thin tapering bottom leg portion 32.The leg l6 and its bottom portion 32 are generally known in the: fieldas a shirttail, and the bottom of the shirttail compared to theruggedness of the tool and its environment is quite thin.

In order to reduce wear on the leg or shirttail bottom 32, hard metalinserts 34 can be placed in the legs 16 but it has been found that evenwith this protection against wear, the tools at the lower leg portionswill wear away unduly because of whipping or other lateral movement ofthe tool imparted to it through the drill string which may extend intothe ground thousands of feet. As stated above, the use of stabilizers onthe drill string and on subs or short sections of string immediatelyabove the tool alleviate the condition to some extent but do not controllateral motion of the tool at the critical point which is the body ofthe tool itself. In order to do this I have provided stabilizer pads 36which may comprise quantities of hard weld metal applied to the upperouter portion of the leg, and if desired, even this hard metal may berendered more wear resistant by the inclusion of nonferrous inserts 38,such as tungsten carbide. It should be noted that the outer surface ofthe stabilizer 36 is preferably on a diameter which coincides with thatof the bottom portions of the legs 16. It should also be noted that therotary cutters 20 describe a circular path the outer diameter of whichcoincides with the outer diameter of the bottoms of the legs in and thestabilizers 36. Therefore, the stabilizers define a diameter which is nogreater than that of the path of the cutters so that the tool will notjam in the formation because of the stabilizers. But by making thediameter defined by the stabilizers the same as that of the cutters andthe bottom portions of the legs lib, the stabilizers not only preventthe tool from rocking or tilting laterally, but provide considerableadditional hard metal wear surface on the tool body itself so that thelife of the tool is greatly increased. The stabilizers provide wearresistant and lateral motion preventing elements but are much morerugged than the thin lower ends or shirttails of the legs l6 and byspacing them about the tool body and placing them only at the criticallocations,

namely directly above and quite close to the legs, the pumping of mudand carrying off of formation cuttings is not interfered with. It mightbe pointed out here that in some tools there are provided outlets 40 fordrilling mud pumped down from the surface and directly upon the rotarycutters 20.

It should of course be understood that changes can be made in the exactform, details and proportions of the construction without departing fromthe spirit of the invention.

I claim:

1. A well-drilling tool for use on the lower end of a drilling stringand having a rotary drill body portion with rotatable cutter meansthereon wherein the improvement comprises: legs on said body portionhaving downwardly and outwardly slanting shirttail portions, the lowerend of said shirttail portions comprising outer diameter surfaces of thetool, said cutters being mounted for rotation on said legs, saidcutters, upon rotation of said body, defining a circular path of cut ofsubstantially the same diameter as the lower end of said shirttailportions, said legs having radially outwardly facing upper portions onsaid body entirely above said cutters and above the bottoms of saidshirttail portions, and hard metal stabilizer shoes on said upperportions of said legs which extend outwardly from said legs tosubstantially the same diameter as said circular path of cut.

2. The structure of claim I, and said legs being integral with theremainder of said body portion, the legs having integral cutter journalsthereon having longitudinal axes, and said stabilizer shoes beingintegral with said drill body portion.

3. The structure in claim 2, and said cutter journals being directeddownwardly and inwardly from the lower ends of said legs, said lowerends of said legs having surfaces of revolution about the bases of saidjournals and concentric to the longitudinal axes of the journals, anddefining, with the outer walls of said legs, relatively thin taperingleg ends, and said stabilizer shoes being in vertical alignment withsaid relatively thin tapering leg ends.

4. A well-drilling tool for use on the lower end of a drilling stringwherein the tool comprises a drill body having a central axis ofrotation and having rotatable cutter means thereon, wherein the bodycomprises an upper section having legs extending downwardly therefrom atspaced points about said axis of rotation, those parts of the drill bodyabove the legs, and radially outwardly facing portions of the drill bodybetween said legs, being of less diameter than a diameter defined by theupper portions of said legs, the legs have radially outwardly disposedfaces slanting outwardly from upper to lower portions thereof, the lowerportions of said legs comprising the outer diameter surfaces of saidtool rotatable cutters being supported by said legs, the cutter, whenthe drill body is rotated, defining a circular path having a diametersubstantially coincident with a circular path defined by the lowerportions of said legs, the upper portions of the legs having stabilizerpads of hard facing material thereon and extending outwardly therefrom,said pads having radially outwardly disposed faces on a circular pathwhose diameter is approximately the same as that of the circular pathdescribed by the lower portions of said legs.

1. A well-drilling tool for use on the lower end of a drilling stringand having a rotary drill body portion with rotatable cutter meansthereon wherein the improvement comprises: legs on said body portionhaving downwardly and outwardly slanting shirttail portions, the lowerend of said shirttail portions comprising outer diameter surfaces of thetool, said cutters being mounted for rotation on said legs, saidcutters, upon rotation of said body, defining a circular path of cut ofsubstantially the same diameter as the lower end of said shirttailportions, said legs having radially outwardly facing upper portions onsaid body entirely above said cutters and above the bottoms of saidshirttail portions, and hard metal stabilizer shoes on said upperportions of said legs which extend outwardly from said legs tosubstantially the same diameter as said circular path of cut.
 2. Thestructure of claim 1, and said legs being integral with the remainder ofsaid body portion, the legs having integral cutter journals thereonhaving longitudinal axes, and said stabilizer shoes being integral withsaid drill body portion.
 3. The structure in claim 2, and said cutterjournals being directed downwardly and inwardly from the lower ends ofsaid legs, said lower ends of said legs having surfaces of revolutionabout the bases of said journals and concentric to the longitudinal axesof the journals, and defining, with the outer walls of said legs,relatively thin tapering leg ends, and said stabilizer shoes being invertical alignment with said relatively thin tapering leg ends.
 4. Awell-drilling tool for use on the lower end of a drilling string whereinthe tool comprises a drill bodY having a central axis of rotation andhaving rotatable cutter means thereon, wherein the body comprises anupper section having legs extending downwardly therefrom at spacedpoints about said axis of rotation, those parts of the drill body abovethe legs, and radially outwardly facing portions of the drill bodybetween said legs, being of less diameter than a diameter defined by theupper portions of said legs, the legs have radially outwardly disposedfaces slanting outwardly from upper to lower portions thereof, the lowerportions of said legs comprising the outer diameter surfaces of saidtool rotatable cutters being supported by said legs, the cutter, whenthe drill body is rotated, defining a circular path having a diametersubstantially coincident with a circular path defined by the lowerportions of said legs, the upper portions of the legs having stabilizerpads of hard facing material thereon and extending outwardly therefrom,said pads having radially outwardly disposed faces on a circular pathwhose diameter is approximately the same as that of the circular pathdescribed by the lower portions of said legs.